From cffe42e72b309a091d648d367a087bd2b9b4f6a3 Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cobrien@witekio.com>
Date: Sat, 4 Oct 2025 14:49:40 +0100
Subject: [PATCH] Create shadow render pass

---
 gpu.c | 66 ++++++++++++++++++++++++++++++++++++++++++++---------------
 gpu.h |  1 +
 2 files changed, 50 insertions(+), 17 deletions(-)

diff --git a/gpu.c b/gpu.c
index 911a83b..65aa425 100644
--- a/gpu.c
+++ b/gpu.c
@@ -393,9 +393,8 @@ void gpu_init(gpu_ctx_t *ctx, GLFWwindow *window, const char *name)
 	}
 
 	// Set up depth image
-	const VkFormat depth_img_fmt = VK_FORMAT_D32_SFLOAT;
 	create_img(
-	    ctx, depth_img_fmt, ctx->swapchain_extent.width,
+	    ctx, VK_FORMAT_D32_SFLOAT, ctx->swapchain_extent.width,
 	    ctx->swapchain_extent.height,
 	    VK_IMAGE_USAGE_DEPTH_STENCIL_ATTACHMENT_BIT,
 	    VK_IMAGE_ASPECT_DEPTH_BIT, &ctx->depth_img, &ctx->depth_mem,
@@ -417,7 +416,7 @@ void gpu_init(gpu_ctx_t *ctx, GLFWwindow *window, const char *name)
 		.pScissors = &scissor,
 	};
 
-	// Set up colour attachment
+	// Attachment configs
 	const VkAttachmentDescription colour_attachment = {
 		.format = surface_fmt.format,
 		.samples = VK_SAMPLE_COUNT_1_BIT,
@@ -428,14 +427,18 @@ void gpu_init(gpu_ctx_t *ctx, GLFWwindow *window, const char *name)
 		.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED,
 		.finalLayout = VK_IMAGE_LAYOUT_PRESENT_SRC_KHR,
 	};
-	const VkAttachmentReference colour_attachment_ref = {
-		.attachment = 0,
-		.layout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL,
+	const VkAttachmentDescription shadow_depth_attachment = {
+		.format = VK_FORMAT_D32_SFLOAT,
+		.samples = VK_SAMPLE_COUNT_1_BIT,
+		.loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR,
+		.storeOp = VK_ATTACHMENT_STORE_OP_STORE,
+		.stencilLoadOp = VK_ATTACHMENT_LOAD_OP_DONT_CARE,
+		.stencilStoreOp = VK_ATTACHMENT_STORE_OP_DONT_CARE,
+		.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED,
+		.finalLayout = VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL,
 	};
-
-	// Set up depth attatchment
-	const VkAttachmentDescription depth_attatchment = {
-		.format = depth_img_fmt,
+	const VkAttachmentDescription render_depth_attachment = {
+		.format = VK_FORMAT_D32_SFLOAT,
 		.samples = VK_SAMPLE_COUNT_1_BIT,
 		.loadOp = VK_ATTACHMENT_LOAD_OP_CLEAR,
 		.storeOp = VK_ATTACHMENT_STORE_OP_DONT_CARE,
@@ -444,15 +447,37 @@ void gpu_init(gpu_ctx_t *ctx, GLFWwindow *window, const char *name)
 		.initialLayout = VK_IMAGE_LAYOUT_UNDEFINED,
 		.finalLayout = VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL,
 	};
-	VkAttachmentReference depth_attachment_ref = {
-		.attachment = 1,
-		.layout = VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL,
+
+	// Create shadow pass
+	const VkRenderPassCreateInfo shadow_pass_config = {
+		.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO,
+		.attachmentCount = 1,
+		.pAttachments = &shadow_depth_attachment,
+		.subpassCount = 1,
+		.pSubpasses = &(VkSubpassDescription){
+			.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS,
+			.pDepthStencilAttachment = &(VkAttachmentReference) {
+				.attachment = 0,
+				.layout = VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL,
+			},
+		},
+		.dependencyCount = 1,
+		.pDependencies = &(VkSubpassDependency) {
+			.srcSubpass = VK_SUBPASS_EXTERNAL,
+			.srcStageMask = VK_PIPELINE_STAGE_FRAGMENT_SHADER_BIT,
+			.srcAccessMask = VK_ACCESS_SHADER_READ_BIT,
+			.dstStageMask = VK_PIPELINE_STAGE_EARLY_FRAGMENT_TESTS_BIT,
+			.dstAccessMask = VK_ACCESS_DEPTH_STENCIL_ATTACHMENT_WRITE_BIT,
+		},
 	};
+	result = vkCreateRenderPass(
+	    ctx->dev, &shadow_pass_config, nullptr, &ctx->shadow_pass);
+	assert(result == VK_SUCCESS);
 
 	// Create render pass
 	const VkAttachmentDescription attachment_descs[] = {
 		colour_attachment,
-		depth_attatchment,
+		render_depth_attachment,
 	};
 	const VkSubpassDependency dependency = {
 		.srcSubpass = VK_SUBPASS_EXTERNAL,
@@ -466,14 +491,20 @@ void gpu_init(gpu_ctx_t *ctx, GLFWwindow *window, const char *name)
 	};
 	const VkRenderPassCreateInfo render_pass_config = {
 		.sType = VK_STRUCTURE_TYPE_RENDER_PASS_CREATE_INFO,
-		.attachmentCount = 2,
+		.attachmentCount = NELEMS(attachment_descs),
 		.pAttachments = attachment_descs,
 		.subpassCount = 1,
 		.pSubpasses = &(VkSubpassDescription){
 			.pipelineBindPoint = VK_PIPELINE_BIND_POINT_GRAPHICS,
 			.colorAttachmentCount = 1,
-			.pColorAttachments = &colour_attachment_ref,
-			.pDepthStencilAttachment = &depth_attachment_ref,
+			.pColorAttachments = &(VkAttachmentReference) {
+				.attachment = 0,
+				.layout = VK_IMAGE_LAYOUT_COLOR_ATTACHMENT_OPTIMAL,
+			},
+			.pDepthStencilAttachment = &(VkAttachmentReference) {
+				.attachment = 1,
+				.layout = VK_IMAGE_LAYOUT_DEPTH_STENCIL_ATTACHMENT_OPTIMAL,
+			},
 		},
 		.dependencyCount = 1,
 		.pDependencies = &dependency,
@@ -833,6 +864,7 @@ void gpu_cleanup(const gpu_ctx_t *ctx)
 	vkDestroyShaderModule(ctx->dev, ctx->model_vert_shader, nullptr);
 	vkDestroyShaderModule(ctx->dev, ctx->frag_shader, nullptr);
 
+	vkDestroyRenderPass(ctx->dev, ctx->shadow_pass, nullptr);
 	vkDestroyRenderPass(ctx->dev, ctx->render_pass, nullptr);
 
 	vkDestroyImageView(ctx->dev, ctx->depth_view, nullptr);
diff --git a/gpu.h b/gpu.h
index c67a68b..ec1c36c 100644
--- a/gpu.h
+++ b/gpu.h
@@ -28,6 +28,7 @@ typedef struct {
 	VkShaderModule frag_shader;
 	VkDescriptorSetLayout desc_set_layout;
 	VkDescriptorPool desc_pool;
+	VkRenderPass shadow_pass;
 	VkRenderPass render_pass;
 	VkPipelineLayout floor_pipeline_layout;
 	VkPipeline floor_pipeline;